1. Field of the Invention
The present invention relates to a door-lock driving system in which door is prevented from being unlocked by a knob when the door has been locked by an electric motor-driven unit.
2. Description of the Related Art
As prior art door-lock driving devices, there are Japanese Patent Application Laid Open No. Sho 58-176374 and Japanese Patent Application Laid Open No. Hei 3-84181. The conventional devices include a knob, a door-lock unit which mechanically carries out a locking or unlocking of a door, a torque transmitting member which operates the door-lock unit, a first electric motor which drives the transmitting unit according to the position of a key inserted into a key switch and a second electric motor which holds a push rod when the door is locked.
However, in the conventional devices, if a great force is applied to the knob after the door has been locked by an actuator in order to unlock the door forcibly while the second electric motor is holding the push rod, the door-lock unit and the second electric motor may suffer damage.